<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>else if 语句</title>
</head>

<body>
    <p>单击按钮以显示基于时间的问候语：</p>

    <button onclick="myFunction()">试一试</button>

    <p id="demo"></p>
    <script>
        function myFunction() {
            var greeting;
            var time = new Date().getHours();
            if (time < 10) {
                greeting = "早安";
            } else if (time < 20) {
                greeting = "日安";
            } else {
                greeting = "晚安";
            }
            document.getElementById("demo").innerHTML = greeting;
        }
    </script>
</body>

</html>